Cascades
by Allegories In Medias Res
Summary: During the war with Kronos, Percy and his friends must battle the most powerful sea monster from Greek mythology. Along the way Percy discovers that he has underestimated the loyalty and power of his friends.
1. Chapter 1

Back on the shore, Annabeth was talking on her cell phone but she hung up as soon as she saw me. She looked pretty shaken.

"It worked," I told her. "The rivers are safe."

"Good," she said. "Because we've got other problems. Michael Yew just called. Under the Williamsburg Bridge, there's a second army coming."

"But I just got the East River god to sink Kronos's ships!"

"It _did_ get sunk, Percy. But there's another monster…One that survived the turnover. Michael said that it suddenly got sucked into the ocean, but after two minutes it resurfaced, and it managed to save about a dozen telkhines, three hellhounds, and about fifty dracaenae. Plus twenty or so demigods. The sea monster is an old one…very old. The one killed by your namesake."

"But I thought that was Med—Oh!"

Thousands of years ago, a hero with my namesake had killed Medusa and then a huge sea monster my dad sent as revenge to some proud queen. He killed it and took the princess as his wife. I looked at Annabeth. "And that monster hasn't reformed since he killed it? Until now?"

She nodded. "The Ethiopian Cetus. I think it's the record reformer. Like at least three thousand years. Just our luck Kronos convinced Oceanus not to send that to your father…though I doubt your dad could actually fight it, with the state of his realm."

I remembered how my father had looked like he'd aged half a century. I grimaced. "Perfect. Any good news?"

"Katie also called. She said that they'd grown a wall of poison ivy so strong it's as powerful as regular concrete. So we don't have to worry about the Brooklyn-Battery Tunnel. And they figured out something else, the Demeter cabin. They figured out how to use waterpowers. See, Demeter is the goddess of agriculture, right? And plants need sunlight, air, and water. If there are plants nearby in need, they can produce those things to help in flourish. Get it?"

"Perfect. Katie could've been one of your siblings. So about the Egyptian Seat…"

"The Ethiopian Cetus, Percy. Yes. The ancient hero used a sword of quartz to kill it. Back then it was very weak. But now it has armor of diamond, Percy. _Diamond._ And diamond is the hardest gemstone in existence. Celestial bronze doesn't even work on it. So how…"

She faltered. A roar shattered the silence of sleeping mortals, followed by three splashes, then another roar that rattled my eyeballs. The Ethiopian Cetus was close by. I grabbed Annabeth's hand. "The only way to fight that thing is underwater. Come on, you're coming with me."

I waded right back into the bay. Annabeth hesitated, and I rolled my eyes. "Come on, Wise Girl."

I grabbed her hand and jerked her into the bay. I made an air bubble for her to breath, and together we followed the sound of the monster roaring underwater.


	2. Chapter 2

The roars of the Cetus sounded even louder underwater. Annabeth gave me a look that clearly meant _Can't you make it quieter?_

I grimaced again. She rolled her eyes and we continued kicking to the monster. Its roars were now making us vibrate so hard I was beginning to get motion sick. I was considering just turning back and going to the Williamsburg bridge and fighting it from there, but then a blue tail the size of a god in giant human form lashed out at us, and I knew we had to fight now.

Annabeth and I circled the monster, trying to get an idea of how large it was. The Cetus was fifty feet tall, its tail being the largest part. It resembled a huge blue sea horse with a horribly oversized tail, teeth the size of a grown man, and two muscular arms with talons that flailed around and gave it scratches in its armor of diamond.

I grabbed Annabeth's hand, kicked to the surface, and clambered onto a rock sticking out of the bay. "Look, Annabeth. It's going to take at least five half-bloods to kill that thing. I can't make an air bubble for them and fight it at the same time. How can we fight it on land?"

Grimly Annabeth pulled out her cell phone, which still worked despite having been underwater the last ten minutes, and said, "Katie? Get your siblings over here. There's a huge sea horse at the Williamsburg Bridge…I mean, like huge. We need help. Percy and I are with the Apollo cabin. The sea monster saved one fifth of the army on the East River. Please, now."

She hung up and held my eyes. "Seaweed Brain, I'll go invisible. You get that thing onto the bridge. Try to drown the rest of the army."

I turned to face the bridge, about twenty feet away. I felt the power of the sea in my gut again. A huge wave picked up the fleet of boats with the surviving army and turned them underwater. I heard a faint cheer from the Apollo cabin, but then the tail of the Cetus surfaced and immediately lifted them out of the water. Annabeth had on her Yankees cap, but I heard her groan behind me. "There's no drowning that army."

So instead I lifted out the army on a block of saltwater and dumped them onto the bridge. Before Blue Seahorse could lift his ugly tail, I lifted in in a cocoon of seawater and slammed it onto the bridge. Quickly I grabbed Annabeth's invisible hand and we kicked to the bridge. The Cetus was thrashing around on it, making seawater splash everywhere. Annabeth and I reached one of the supports on the water and we scaled it. Above our heads was solid concrete, but I used Riptide to saw a hole for us to clamber through.

The Cetus saw us for the first time. Its eyes, the size of footballs, found mine and I froze. The eyes kept changing colors. They flickered until suddenly it stopped at a shade of fuchsia. The color slowly melted into chartreuse, and then dissolved into the shade of Annabeth's hair. I faintly heard the Apollo cabin calling me to help, but the Cetus's eyes hypnotized me, making me want to see what color it would change to next.

Annabeth saved me. She jerked me and then banged the hilt of her dagger on my head. "Earth to Seaweed Brain!"

Stars were popping in front of my eyes. "Sorry…Its eyes hypnotized me."

"What do you mean they hypnotized you? Has your brain finally melted into horse poop?"

Anger surged through me. I turned to face her. She'd taken off her Yankees cap and was glaring at me. "Why don't you look at them and try to turn away?"

The fury in her face disappeared. "Whatever. But we've got to—DUCK!"

A mass of talons swung at us. I fell to the ground and held up Riptide, trying to saw off some of its talons. I managed to shatter the tip of one of them. The Cetus roared so loud I temporarily went deaf. When my ears stopped ringing, the Cetus wasted no time getting revenge. It swatted me so vigorously that Riptide went off the edge of the bridge. My sword wouldn't come back for a few minutes.

Just then a branch of thorns went flying by my ear. "Sorry, Percy!" shouted a new voice.

Katie had marched her cabin to the Williamsburg Bridge. I couldn't see Annabeth, but a dracaenae was flailing around, trying to grab thin air. I stood up. It was going to be the first long night of a tiring war.


End file.
